Effect Of Boron Residue On Reuse Performance Of Gas Fracturing Return Fluid In Shale

Fracturing technology has become an important measure to increase oil and gas production.At present,the main fracturing fluid is guanidine gum water-based fracturing fluid.The amount of water used to prepare fracturing fluid is large,and there is usually a shortage of water resources around the fracturing site.It has become a hot issue of oil and gas field environmental protection to explore the reuse of fracturing backflow after treatment.The components of the flowback fluid are complex,and there are many factors affecting its reuse,such as high-value metal ions,boron ions,etc.,especially boron.Taking the performance index of fracturing fluid as the assessment index,it is of great significance to determine the allowable maximum concentration limit of boron in the fracturing flowback fluid after treatment to improve the water return rate after treatment and establish an economic and feasible sewage treatment process.Paper base fluid viscosity as examining index,discusses the distilled water,tap water,water,long six long simulation water,flowback fluid simulation,processing of fracturing fluid flowback after the effects of boron concentration of guanidine gum swelling rate,sleeping on the determination of the base fluid viscosity of fracturing fluid,heat resistance performance,win naing shear resistance,determine the upper limit of the residual concentration of boron;The influence of the preparation of fracturing fluid on the upper limit concentration of boron ion and the upper limit of the maximum content of the above ions in the flowback fluid were studied when the concentration of Ca²⁺,Mg²⁺,CO₃^2-,HCO₃^-,Na⁺,Cl^-and SO₄^2-was1000 mg/L.The effects of 200 mg/L Ba²⁺and Sr²⁺on fracturing fluid properties were verified.The viscosity,temperature resistance,temperature and shear resistance,gel breaking and sand suspension properties of the base solution were determined.The results showed that:on the premise of ensuring the performance of the fracturing fluid,the upper limit of boron concentration in the water was 5 mg/L.At this value,the order of ions that influence the temperature resistance of the fracturing fluid was:Mg²⁺>Ca²⁺>Na⁺>HCO₃^->SO₄^2->Cl^-.The highest concentrations of Ca²⁺,Mg²⁺,CO3^2-,HCO₃^-,Na⁺,Cl^-,SO₄^2-,Ba²⁺and Sr²⁺in water were 800 mg/L,800 mg/L,0 mg/L,1 000 mg/L,65 000 mg/L,100 000 mg/L,250 mg/L,200 mg/L and 200 mg/L,respectively.The viscosity of guanidine base solution is 51⁵4 mPa·s.When the boron content in distilled water is 5 mg/L,the performance of the fracturing fluid prepared after the above ion concentration is added is as follows:Base fluid viscosity of 51⁵4 mPa s.,heat-resistant ability is greater than 70℃,the shear resistance is greater than 60 min,rheological parameter 0.0812﹤n﹤0.3691,31.24640 mPa,31.24640 mPa·sⁿ﹤K﹤62.29598 mPa·sⁿ,carrier performance is0.401 mm/s⁰.591 mm/s,gel breaking liquid viscosity,less than or equal to 2 mPa s,residue content,less than 360 mg/L,the interfacial tension is less than 1 mN/m,surface tension is less than 22 mN/m,to meet the requirements of the site for recycling.